Method and device for compaction of a track ballast bed

Abstract

A method for compaction of a track ballast bed uses a tamping unit including two oppositely positioned tamping tools which are actuated with vibrations and are lowered into the track ballast bed during a tamping operation and moved towards one another with a squeezing motion. A progression of a force acting upon the tamping tool over a path covered by the tamping tool is recorded during a vibration cycle by sensors disposed at the tamping unit for at least one tamping tool. At least one characteristic value is derived therefrom and used to carry out an evaluation of the tamping operation and/or of a quality of the track ballast bed. The tamping unit is thus used as a measuring apparatus during operative use. A device for performing the method is also provided.

The invention claimed is: 
     
       1. A method for compaction of a track ballast bed, the method comprising the following steps:
 actuating two oppositely positioned tamping tools of a tamping unit with vibrations, lowering the tamping tools into the track ballast bed during a tamping operation and moving the tamping tools towards one another with a squeezing motion superimposed with vibration cycles of rapid opening and closing of the tamping tools with a small amplitude; 
 using sensors disposed at the tamping unit to record a progression of a horizontal contact force to ballast of the ballast bed acting upon at least one of the tamping tools over a vibration path covered by the tamping tool during an individual vibration cycle superimposed on the squeezing motion; 
 deriving an inclination of the progression during a relief phase of the tamping tool as at least one characteristic value from the recorded progression; and 
 carrying out an evaluation of at least one of the tamping operation or a quality of the track ballast bed by using the at least one characteristic value. 
 
     
     
       2. The method according to  claim 1 , which further comprises using the characteristic value as a parameter for controlling the tamping unit. 
     
     
       3. The method according to  claim 1 , which further comprises deriving a maximal force acting on the tamping tool during the vibration cycle as a first characteristic value for evaluation of a ballast condition or a compaction condition of the ballast bed. 
     
     
       4. The method according to  claim 3 , which further comprises deriving a vibration amplitude occurring during the vibration cycle as a second characteristic value for evaluation of a compaction condition of the ballast bed. 
     
     
       5. The method according to  claim 4 , which further comprises determining a start of contact between the tamping tool and the ballast and a loss of contact between the tamping tool and the ballast for the vibration cycle to evaluate a ballast condition of the ballast bed, and deriving a third characteristic value from the evaluated ballast condition. 
     
     
       6. The method according to  claim 5 , which further comprises deriving an inclination of the progression during a stress phase of the tamping tool as a fourth characteristic value for evaluation of a load bearing capacity of the ballast bed. 
     
     
       7. The method according to  claim 6 , which further comprises deriving the inclination of the progression during the relief phase of the tamping tool as a fifth characteristic value for evaluation of a ballast condition of the ballast bed. 
     
     
       8. The method according to  claim 7 , which further comprises deriving a deformation work performed by the tamping tool from the recorded progression as a sixth characteristic value for determining a degree of utilization. 
     
     
       9. The method according to  claim 8 , which further comprises deriving an overall inclination of the progression as a seventh characteristic value for determining an overall stiffness of the ballast bed. 
     
     
       10. The method according to  claim 9 , which further comprises determining the overall inclination by linear regression of the recorded progression. 
     
     
       11. The method according to  claim 1 , which further comprises:
 recording the progression of the force acting on the tamping tool over the path covered by the tamping tool for several vibration cycles of a tamping operation; 
 determining a characteristic value for each of the vibration cycles; and 
 carrying out an evaluation procedure by using a characteristic value progression. 
 
     
     
       12. The method according to  claim 1 , which further comprises:
 performing a plurality of squeezing operations at a track location; 
 determining a characteristic value for a vibration cycle or a characteristic value progression for several vibration cycles for evaluation of a compaction condition of the ballast bed for each squeezing operation; and 
 performing a further squeezing operation upon non-attainment of a prescribed compaction condition. 
 
     
     
       13. The method according to  claim 1 , which further comprises:
 determining a characteristic value for a vibration cycle or a characteristic value progression for several vibration cycles for each of a plurality of tamping operations at different locations along a track; and 
 carrying out an evaluation of a spatial development of at least one of a compaction result or the quality of the ballast bed from the characteristic value or the characteristic value progression. 
 
     
     
       14. A device for compaction of a track ballast bed, the device comprising:
 a tamping unit including two oppositely positioned tamping tools covering a path; 
 a squeezing drive for a squeezing motion of the tamping tools; 
 a vibration drive for generating vibrations cycles of rapid opening and closing of said tamping tools with a small amplitude superimposed on the squeezing motion; 
 pivot arms each coupling a respective one of said tamping tools to said squeezing drive and said vibration drive; 
 sensors disposed at least at one of said pivot arms or said tamping tool associated with said one of said pivot arms for recording a progression of a horizontal contact force to ballast of the ballast bed acting on said tamping tools over a vibration path covered by said tamping tools during an individual vibration cycle superimposed on the squeezing motion; and 
 an evaluation device receiving measuring signals from said sensors, said evaluation device being configured for determining an inclination of the progression during a relief phase of the tamping tool as a characteristic value derived from the progression. 
 
     
     
       15. The device according to  claim 14 , which further comprises a tamping tool mount, and at least one force-measuring sensor disposed in said tamping tool mount.